One of the main envisaged means to increase a cellular network's capacity significantly beyond 4G's capabilities is by densification of the radio access network (RAN). Essentially, densification of the network's infrastructure brings the network access points closer to the end user. A denser radio access network infrastructure implies an average lower path loss, thereby yielding a better link budget, and an average lower number of users served by each access point. Such densification is widely believed to bring substantial gains in network data throughputs (it has already done so in the past decades), but also to help reducing the networks' energy consumption. The related art 3GPP standards organization has already started to look into the integration of denser small-cell deployments within the current 4th generation of cellular architecture, the Long Term Evolution (LTE) system.
A second key feature of future radio access technologies is flexible usage of frequency spectrum, with a typical network node supporting not only a potentially new 5G standard operating in new frequency bands (e.g., at mmWave frequencies), but also capable of integrating different radio access technologies (RATs) operating at different frequency bands, such as numerous releases of the 4G LTE standard, a variety of WiFi, etc. Therefore, spectrum flexibility may bring benefits in terms of increased data rate (e.g., when multiple spectrum bands are aggregated), but also benefits in terms of efficient spectrum usage and interference mitigation (e.g., when frequency bands are entirely or partially released by lightly loaded access nodes). To fully capitalize these benefits, however, new resource management algorithms should exploit the inherent couplings between RAN densification and dynamic spectrum allocation.
Traditional communication systems' network nodes, such as base stations in 2G-4G radio cellular systems, are designed to operate within certain frequency spectrum bands with a fixed transmission power output, regardless of the time-variations of traffic demand and user mobility patterns. In more advanced 4G systems, such as the 3GPP LTE-A, carrier aggregation mechanisms have been introduced to support higher peak data rate for the system users. Carrier aggregation allows a base station of the system to activate/deactivate frequency carriers in a fast time-scale depending on the data rate and traffic requirements of the users.
The optimization of access node placement in an area and their configuration in terms of transmission power output, spectrum/frequency allocation, etc. is also known as network planning. The aim of network planning is to primarily guarantee network coverage and capacity based on average traffic derived from population and geographical maps along with driving tests prior to a network operation. To increase capacity at user dense areas, hierarchical network planning is used which implies multi-tier networks where each tier consists of a different type of access node with different transmit power and coverage characteristics.
The configuration the spectrum band(s) where each network node shall operate is often referred to as frequency re-use planning. Typically, the frequency band is globally assigned to the entire network (1 frequency reuse case). However, when network nodes utilize the entire frequency band with uniform power distributed across the available bandwidth, they create strong interference to cell edge users of neighbouring network nodes. More advanced forms of frequency reuse have been envisaged to remedy this, including fractional frequency reuse and soft frequency reuse. All these approaches introduce a method where spectrum resources are divided so as interference between networks nodes is reduced to a minimum.
A general drawback of conventional techniques with statically or semi-statically radio resource assigned to system entities is that an excess of resources (e.g., frequency bandwidth) may be provided to lowly-loaded access nodes, thereby creating unnecessary interference to other access nodes, or, vice versa, insufficient resources be provided to highly loaded access nodes. An additional general drawback of radio resource management (RRM) of conventional solutions is that it is traditionally dimensioned and rigidly designed for sparse deployments of network nodes (e.g., base stations, access points, etc.). As such, these techniques cannot handle the complexity of radio resource management in ultra-dense radio access networks with hundreds of network nodes deployed in close proximity, nor provide the degree of flexibility in the radio resource allocation that is required in such networks to assure an efficient network operation.